This invention relates to a process for defending objects emitting an infrared radiation, in particular ships, against missiles, which are equipped with intelligent, in particular, scanning, imaging, correlating and/or spectral filtering infrared seeker heads, and droppable bodies to carry out the process.
It is well-known to defend water borne, land borne or airborne; objects emitting an infrared radiation, in particular ships but also airplanes and tanks, against missiles equipped with infrared seeker heads, in that upon detection of the approach of a missile one or more protechnic fake target clouds are launched in succession by means of droppable bodies in the air space adjacent the object, the clouds guiding the infrared seeker head of the missile from the object and towards themselves. For example, reference is made to European Patent No. 0 240 819 wherein droppable bodies generating fake targets are placed and ignited in such a manner at specified times in predetermineed spatial regions that the generated fake targets lie on a deflection curve at specified intervals in time and space and are to be steered towards in such a manner in succession by the missile that its flight path passes over in the deflection curve and finally in the direction of deflection.
The fake target clouds comprise burning phosphorus flares, such as plates or strips which are coated with red phosphorus and which are ejected from the droppable body at a predetermined height at the desired point and in so doing are ignited.
However, the goal of the latest development in infrared seeker heads is to make the seeker heads "intelligent" and thus to make them immune to conventional infrared fake targets, i.e., to design them in such a manner that they respond to the object signature, in particular the ship signature. The development is proceeding in different directions. Thus, for example, for the imaging "gated video - target seeker heads" an adaptive "tracking gate" is used, which can be adapted accurately to the size of the targeted ship by means of video processors and suitable algorithms. The viewing window of the seeker head can be reduced after locking on the ship size, with the result that fake target clouds, which are generated outside this adaptive window, thus above or next to the ship, remain ineffectrive.
For the "correlation trackers" a human operator usually locks on the target. After locking on the object, the seeker head then finds by means of comparison (cross correlation) of two successive images (stored reference image/actual image) its way unimpeded into the target, even if infrared fake target clouds are produced in the vicinity of the target.
Another method to eliminate false targets consists of a frequency analysis by means of the seeker head, which can distinguish between the radiation characteristics of the infrared radiators (for example ship engines) of the target that exhibit a comparatively low temperature and the radiation characteristics of a hot fake target cloud. Thus, in summary the known infrared fake target clouds are not in a position to defend an object against missiles equipped with intelligent seeker heads.